Furnace



Oct. 15, 1929.

H. H. DIGGINS FURNACE Filed April 2, 192B 2 Sheets-Sheet 1 J7! a v'cto 7", 7! 14 Oct. 15, 1929. H. H. DIGGINS FURNACE Filed April 1928 2 Sheets-Sheet. 2

Patented Oct. 15, 1929 PATENT OFFICE EABTE H. DIGGINS, OI WOODSTOCK, ILLINOIS ruanacn Application filed April 2, 1928. Serial No. 286,497.

The present invention relates particularly ,to warm air heating systems in which the heat energy is obtained from liquid or gaseous fuels; and it has for its object to produce a simple and novel furnace of high efiiciency. A subsidiary object of the present invention is to produce a simple and novel warm air furnace in which the gaseous products of combustion are directly opposite the most highly heated air and, in cooling, come opposite cooler and cooler zones in the air stream; whereby the products of combustion, in passing to the discharge outlet, always give up heat to the air and at no time are 'heated'by the air. 4

Further objects of the present invention are to produce a firebox for a warm air furnace that will permit the air to flow through the furnace without meeting any material resistance; so to proportion t e firebox and the enclosing casing that the expansion of the air'as it is heated, instead of producin back pressure, is effectively applied to creating an upflow and to make it possible for each warm air pipe to obtain its own supply of air inde endently of the other pipes.

further object of the present invention is to be so arran ed that any of the various types of gas or oi burners may be applied thereto.

The various features of novelty whereby my invention is characterized will hereinafter be pointed out with particularity in the claims; but, for a full understanding of my invention and of its objects and advantages, reference may be had to the following detailed description taken in connection withthe accompanying drawings, wherein: 40

shell of a furnace arranged in accordance with my invention, in its imtial condition; Fig. 2 is a rspective view, on the same scale as Fig. 1, o my improved firebox before it is assembled in the furnace; Fi 3 is a longitudinal vertical central section t rough an assembled furnace equipped with an oil burnin apparatus entering the same from the nt, near the bottom; and Fig. 4 is a section taken 0 approximately on line 4-- 4 of Fig. 3.

' the interior of a forwardlyprojecting tubular reduce a furnace that will not only be simp e in construction but be inexpensive and p vpgss into the firebox from the front, near the Figure 1 is a perspective view of the outer Referring to the drawin 1 represents a firebox in the form of a tu of any desired length and of stream line cross-section; the ends of the tube being closed by means of suitable heads. If the firebox is comparatively short, the body portion may be made of a single sheet bent in tubular form and having its meeting edges welded together or riveted and welded together. Longer fires boxes will require more than one sheet and may be regarded as bein composed of sections secured together, en to end. 'The firebox is supported with its thick end toward the bottom and its narrow tapered end at the top, conveniently by setting the box on suitable saddles 2. In the front end wall 3 of the firebox, at a considerable distance above the bottom, is a large man hole 4 that places the interior of the firebox in communication with member 5. In therear wall 6 of the firebox aretwo outlets for the combustion gases, one arranged near the 4 bottom and the other a short. distance below the top of the-firebox. Flues 7 and 8 are connected to these discharge outlets, the flue 7 being at the bottom and the flue 8 at the top.

The'man hole in the front of the firebox is rimarily intended .for the purpose of giving access at all times to the interioi of the firebox, although there are some kinds of burners that it ma" be necessary to fix in this man hole. Most o the burners at present used will ttom, or up through the bottom. It is a simple matter to cut a hole in the front bottom wall of the firebox to receive the kind of burner desired when every furnace is being installed.

The shell or casing of the furnace is a boxlike structure adapted to beset over the firebox; being spaced apart from the walls of the latter at the sides and at the ends. Any suitable means may be provided for admitting air into the bottom of the casing underneath the firebox. 4

In the arrangement shown, the casing consists of sides 9 and 10,-front and rear walls 11 and 12 and a top wall -13. Each wall may be made of a single sheet, all of the walls being 10- secured together by means of a frame 14 of angle irons or other suitable structural shapes; In the front wall of the casing is a hole 16 through which the tubular member 5 on the firebox may extend; while in the rear wall are openings through which the flues 7 and 8 may extend.

In the arrangement shown, there is no bottom to the casing, the four upright corner pieces of the frame projecting down below the bottom edges of the side and front walls of the casing, so as to support the lower edges of these walls above the floor and thus permit cod air to enter beneath the firebox from all 51 es.

The side walls of the casing or shell are gradually curved inwardly from the bottom toward the top, so that the top wall is long and narrow, being only very little wider than the diameter of the pipes for carrying warmed air throughout a house. The top wall is provided with a series of large holes 17 distributed lengthwise thereof, each hole being adapted to have a warm air pipe 8 associated therewith.

It will be seen that the warm air pipes rise vertically directly above the firebox, so that air that rises up past both sides of the firebox flows directly-into the warm air pipes without deflection and without encountering resistance of any kind. Furthermore, since the air rises vertically past the firebox, each warm a1r pipe receives air from a particular zone. In other words, the air supply to each pipe is about as independent of the remaining air delivered by the furnace as though there were vertical partitions across the air space in the furnace to compel the air rising in that zone lying beneath each pipe to be delivered to that pipe.

The burner is placed in the front end of the firebox, preferably at the bottom. If a lining of fire brick is required, the brick may simply be set in without cementing. In the arrangement shown, there is a conventional burner apparatus 20 having a tubular nozzle 21 passing through the front walls of the casing and the firebox below the man hole; and there is a brick lining 22 set in the bottom of the firebox at the front end.

It will be seen that the flame and hot combustion gases rise to the top in the front of the firebox, when the fire is burning. The hot gases travel rearwardly along the top of the firebox and then are deflected downwardly. If the chamber 23 in the top smoke flue 8 is closed, the gases cannot escape from the firebox in this region, and they'must therefore continue downwardly. However, it will be found that the conditions that are set up in the firebox will cause the combustion gases to travel toward the front after they have dropped down some distance in the rear end of the firebox, thus coming in contact with theflame and causing unburned portions of the fuel, that have been carried along by the combustion gases, to be ignited. In short, there will be a circulation of the combustion gases, and perhaps one or more re-circulations, so that there is very little likelihood of any unconsumed fuel remaining in the combustion gases by the time that they have been forced down into the bottom at the rear end of the firebox, so asto be permitted to escape through the lower flue 7. Consequently practically perfect combustion will be obtained.

It will be seen that the hottest part of the firebox is at the top; the flame and hot gases rising directly to the top and flowing along the same and also gradually passing down along the side walls. The coolest combustion gases are those at and in the bottom of the firebox. Therefore, the coolest gases are in the zones where the air to be warmed first comes in contact with the walls of the firebox. The comparatively cool gases are still much warmer than the cool air, so that some of the heat of the cool gases is transferred to the air. As the slightly warm air rises, it comes in contact with walls whose temperature inc'reases with the elevation, because the gases in the firebox become hotter and hotter as the top is approached. It will thus be seen that the air to be warmed and the combustion gases to be cooled pass in opposite directions on opposite sides of the heated walls of the firebox, the hottest gases and the hottest air being at the top and the coolest gases and the cold air being at the bottom. By this arrangement, the heat energy from the fire is most efliciently transferred to the air and the hottest heat interchanging surfaces are available for delivering heat to the air just before it leaves the furnace.

It will be seen that a plane tangent to one of the sides of the firebox makes a gradually increasing angle with the longitudinal central plane of the fire box, as this tangent plane is moved upwardly along the side. It will also be seen that the transverse width of the air space between the sides of the firebox and the casin increases gradually from a. point near the bottom. The result is that as the rising air is further heated and further expanded, the effect of the expansion is not to produce a back or downward pressure but the resultant will be an upward force. Furthermore, since heat is radiated at right angles to the surface from which it is emitted, it will be seen that these lines of radiation, while almost horizontal toward the bottom of the firebox, swing gradually toward the vertical. Therefore, since an effect of the radiation is that of a force pushing in the same direction, it will be seen that there will be a gradually increasing vertical component to such force as the top reached, and therefore the air will be assisted in rising up past the firebox, by a driving with particularity form of my invention, I do not desire to be force that is entirely independent of the forces within the air itself.

While I have illustrated and described only a single preferred limited to the exact structural details thus illustrated anddescribed; but intend to cover all forms and arrangements which come within the definitions of my invention constituting the appendedclaims.

I claim 1. In an air heater, a fire box in the form of a shell of stream line shape in vertical section, a casing over said fire box, said casing having an air inlet at the bottom and an outlet at the top, the upper parts of the sides of the casing converging from the bottom toward the top but at a smaller angle than the corresponding sides of the fire box.

2. In combination, a furnace having a narrow vertical air heating chamber, said chamber increasing gradually in width from near the bottom to the top, and air pipes connected to-the top wall of said chamber with their long axes parallel with the path of movement of the heated air approaching the pipes.

In testimony whereof, I sign this specification.

HARTE H. DIGGINS. 

